Future diesel oxidation catalysts (DOC) will need to perform effectively at increasingly low exhaust temperatures as a result of continued improvements in diesel engine efficiency. An ultimate goal is to achieve over 90% conversion below 150° C., the so-called “150° C. challenge”. Recently, progress has been made in designing catalytic materials with enhanced low-temperature oxidation performance, such as by combining gold and silver nanoparticles with copper, manganese, or iron. However, significant technical barriers need to be surmounted before such novel materials are ready for commercial use. In particular, such novel materials tend to underperform when subjected to harsh reaction environments typical to automotive emissions. Alternatively, increasing precious metal loading (e.g., Pt) can improve the low-temperature performance of current commercial catalysts, but such an approach is cost-prohibitive.
The impact of ZrO2 supports on CO and C3H6 oxidation, sulfur tolerance, and hydrothermal stability was recently investigated, e.g., Appl. Catal. B187 (2016) 181. A strong interaction between Pd and ZrO2 resulted in a greater thermal stability, as evidenced by good oxidation performance even after aging at 800 and 900° C. for 16 hours; however, Pd/ZrO2 is known to suffer performance loss due to ZrO2 phase transformation. Thus, further improvements in hydrothermal stability and low-temperature performance would be of great benefit to diesel oxidation catalysts.